Losartan potassium is blood pressure reducing angiotensin receptor blocker which is commercially available in tablet forms as a single active ingredient medication (COZAAR®) and also in combination with the diuretic hydrochlorothiazide (HYZAAR®). These tablets are formulated with partially pre-gelatinized corn starch, the function of which is to act as the tablet disintegrant facilitating active ingredient gastric release.
Losartan potassium readily dissolves in neutral to basic media. However, in acidic media, the salt dissociates and the losartan free acid precipitates as a gel layer around the tablet. The gel layer can result in insufficient tablet disintegration of immediate release tablets containing losartan potassium and chlorthalidone, and therefore, insufficient active ingredient release. In order to meet immediate release criteria, effective tablet disintegration in the acidic gastric environment is essential for chlorthalidone, since chlorthalidone has low solubility across the physiologic pH range.